How many bytes are used to store a null value in an nvarchar(n) column?

Question

We are designing a new database, and need to know if a nvarchar(n) column will use any bytes to store a null value?

If a nvarchar(n) column stores a null value, how many bytes are used?
How many bytes are used to store and empty string in a nvarchar(n)? (i.e."")

Possible duplicate of [How are NULLs stored in a database?](https://stackoverflow.com/questions/254152/how-are-nulls-stored-in-a-database) — Piotr Palka, Sep 20 '19 at 15:59

score 0 · Answer 1 · answered Sep 20 '19 at 16:05

0

Empty string will use 2 bytes. More details at: nchar-and-nvarchar
NULL will use 1 bit in the NULL bitmap.

answered Sep 20 '19 at 16:05

Piotr Palka

2,913
1
8
16

score 0 · Answer 2 · answered Sep 20 '19 at 16:12

0

It is a physical implementation detail, so it could be different for Oracle an for SQL Server. With SQL Server, NULLs a represented with a single bit in the null bitmap (one bit for each nullable column). An empty string, be it varchar or nvarchar, it's two bytes. Hope someone from Oracle side will complement.

answered Sep 20 '19 at 16:12

dean

9,590
2
20
24

2

_"Hope someone from Oracle side will complement"_. In Oracle, a `null` value takes 1 byte in block, unless it is at the end of the row (or all the values following it in the row are all `null` as well), in which case it takes zero bytes. – Matthew McPeak Sep 20 '19 at 18:20

How many bytes are used to store a null value in an nvarchar(n) column?

2 Answers2